Search engine Google has deployed 4,000 Linux servers, with plans to increase to 6,000 this year, making it possibly the largest Linux installation in the world.

Google said it turned to Red Hat Linux primarily because of the cost. The OS itself costs nothing, compared with $500 to $900 per server for Windows servers. And the hardware is also cheap; Red Hat runs on commodity white-box PCs rather than more expensive RISC Unix servers.

“The hypertext analysis is computationally expensive; we need to have an efficient system for doing that. That’s why we use a lot of cheap PCs. It’s a cheaper platform. The dollar per MIPS is better for PCs,” said Sergey Brin, founder and president of Google.com.

Support was another factor in choosing Linux, Google said. The company has Linux expertise in-house, and values the ability to look at the source code to correct problems, rather than having to rely on a vendor. And where the in-house expertise fails, Google has found the Linux community responsive with fixes.